Multiscale Composites Research Articles

Effects of ozonized carbon black on fracture and post-cracking toughness of carbon fiber-reinforced epoxy composites

Improving the fracture and post-cracking toughness of carbon fiber-reinforced composites based on thermosetting epoxy matrices are of significant interest in a wide range of applications. Herein, we report the synergistic integration of multi-scale composites by combining nano-scale filler and macro-scale fiber reinforcement inspired by the hierarchy approach. For the nano-scale filler, the carbon black (CB) surface was successfully modified using ozone treatment and thereby achieved highly efficient dispersion and interfacial properties. The reinforcing mechanisms were also analyzed, and the improvements on dispersion and interfacial properties should mainly be attributed to mechanical interlocking effect. For all of the multi-scale composites fabricated, the ozone-functionalized CB content was found to be optimal at 5 wt%, which improved the fracture and post-cracking toughness by 12.5% and 61.9%, respectively, compared with pristine CB.

Editorial: Multiscale Lattices and Composite Materials: Optimal Design, Modeling and Characterization

The Research Topic “Multiscale lattices and composite materials:” (MLCM) is focused on the optimal design, modeling, and characterization of novel lattices, composite materials, and structures at different scales, through the control of the internal architecture of the system. A fundamental goal of this article collection is the study of mechanical metamaterials that are able to form next-generation-generation cellular solids; lattice materials, multiscale composites; and structural-scale systems. The collection took inspiration from the peculiar behaviors exhibited by structured materials at multiple scales (Bosia et al., 2018). The latter include, for example, high stiffness, strength, and toughness at extremely low densities (Meza et al., 2014), phononic band-gaps (Lu et al., 2009), sound control ability (Cummer et al., 2016); negative effective mass density (Liu et al., 2000); localized confined waves (Theocharis et al., 2013), to name but a few examples. The research reported devoted special attention to the creation of complex mechanical systems with properties derived mainly from their geometric design rather than their chemical composition (Cummer et al., 2016; Bertoldi et al., 2017). Also investigated was the use of multiscale lattices to optimally design reinforcing elements for novel composite materials (Fleck et al., 2010; Li et al., 2014). The chosen modeling and experimental approaches were able to predict and characterize the intrinsically complex mechanical behavior of the analyzed systems through multiscale techniques.

Novel Multi-Scale Cementitious Composites Developed Using Microcrystalline Cellulose (MCC) and Sisal Fibers

Novel Multi-Scale Cementitious Composites Developed Using Microcrystalline Cellulose (MCC) and Sisal Fibers

Improved static and dynamic mechanical properties of multiscale bucky paper interleaved Kevlar fiber composites

Herein, the influence of bucky paper interleaves and dispersed MWCNT network on static and dynamic mechanical properties of Kevlar-epoxy composites, subjected to different loading conditions is investigated. Multiscale hybrid laminar Kevlar composites are prepared by vacuum impregnation followed by compression moulding technique. Subsequently, these hybrid composites are subjected to tensile, flexural, dynamic mechanical and low velocity impact and directly compared with basic Kevlar composite (KE) laminate. It is found that bucky paper interleaves along with dispersed MWCNT (KEBC) improve interlaminar and interfacial properties respectively. It is found that the maximum dynamic impact energy absorption and load carrying capacity of KEBC increase to 13.8 J and 2650 N respectively which shows an overall improvement of 31% over KE. These results are further confirmed by Charpy's impact test, in which maximum impact toughness reaches to 90.4 J/mm2, which is consistent with dynamic impact test results. After conducting various lab scale mechanical tests, ballistic test is also performed over KEBC and KE. It is found that, in case of KEBC, back face signature is reduced to 30% over KE, which confirms the collective effort of bucky paper interleaves and dispersed MWCNT in enhancing the energy absorption capability of hybrid laminar composite.

Enhancing the Viscoelastic Performance of Carbon Fiber Composites by Incorporating CNTs and ZnO Nanofillers

Carbon fiber reinforced plastic composites (CFRPs) possess superior elastic mechanical properties. However, CFRPs lack sufficient viscoelastic performance, such as damping and creep resistance. In an effort to improve these properties, in this study, hybrid multiscale composites with various combinations of zinc oxide nanorods (ZnO) and carbon nanotubes (CNTs) were deposited at the interface of carbon fiber laminae. The viscoelastic properties of the corresponding composites were characterized via dynamic mechanical analysis (DMA) during both temperature and frequency sweeps. The creep activation energy for each composite configuration was also calculated. The DMA temperature sweep analysis reported that the composite incorporating both ZnO and CNTs exhibited the highest improvements in all viscoelastic properties. This composite also attained better creep resistance, evident by the highest activation energy. The DMA frequency sweep analysis revealed that composites incorporating a single nanofiller improves the viscoelastic properties more than the combined nanofiller composite. Despite these improvements in the viscoelastic properties, the non-uniform dispersion and agglomerations of the nanofillers affected some of the elastic properties negatively, such as the storage modulus.

Effective properties of hierarchical fiber-reinforced composites via a three-scale asymptotic homogenization approach

The study of the properties of multiscale composites is of great interest in engineering and biology. Particularly, hierarchical composite structures can be found in nature and in engineering. During the past decades, the multiscale asymptotic homogenization technique has shown its potential in the description of such composites by taking advantage of their characteristics at the smaller scales, ciphered in the so-called effective coefficients. Here, we extend previous works by studying the in-plane and out-of-plane effective properties of hierarchical linear elastic solid composites via a three-scale asymptotic homogenization technique. In particular, the approach is adjusted for a multiscale composite with a square-symmetric arrangement of uniaxially aligned cylindrical fibers, and the formulae for computing its effective properties are provided. Finally, we show the potential of the proposed asymptotic homogenization procedure by modeling the effective properties of musculoskeletal mineralized tissues, and we compare the results with theoretical and experimental data for bone and tendon tissues.

Nonlinear vibration analysis of multiscale doubly curved piezoelectric composite shell in hygrothermal environment

This research studied large amplitude vibration behaviors of multiscale composites doubly curved shells with piezoelectric layer. By using Reddy’s third-order shear deformation theory, the strains and stresses are obtained. According to the Halpin–Tsai model three-phase composites layers are considered. The governing equations of the multiscale doubly curved shell are derived by implementing the Hamilton’s principle and are solved via homotopy perturbation method. For investigating correctness and accuracy, this article is validated by other previous studies. Finally, the influence of different parameters such as temperature rise, various distributions pattern, applied voltage, magnetic potential, and aspect and curvature ratio are observed in this article. It is found that these parameters have significant influence on nonlinear frequencies.

Preparation and Mechanical Properties of Graphene/Carbon Fiber-Reinforced Hierarchical Polymer Composites

Conventional carbon fiber-reinforced plastics (CFRP) have extensively been used as structural elements in a myriad of sectors due to their superior mechanical properties, low weight and ease of processing. However, the relatively weak compression and interlaminar properties of these composites limit their applications. Interest is, therefore, growing in the development of hierarchical or multiscale composites, in which, a nanoscale filler reinforcement is utilized to alleviate the existing limitations associated with the matrix-dominated properties. In this work, the fabrication and characterization of hierarchical composites are analyzed through the inclusion of graphene to conventional CFRP by vacuum-assisted resin infusion molding.

Electrical self-sensing of strain and damage of thermoplastic hierarchical composites subjected to monotonic and cyclic tensile loading

Electrical monitoring of strain and damage in multiscale hierarchical composites comprising unidirectional aramid fibers modified by multiwall carbon nanotubes and polypropylene as matrix is investigated. The key factor for electrical self-sensing in these thermoplastic composites is the formation of a multiwall carbon nanotube network, which is achieved by using two material architectures. In the first architecture, the multiwall carbon nanotubes are dispersed within the polypropylene matrix, while aramid fibers remain unmodified. The second architecture uses also multiwall carbon nanotube-modified polypropylene matrix, but the aramid fibers are also modified by depositing multiwall carbon nanotubes. Under tensile loading, the electrical response is nonlinear with strain ( ε), and the piezoresistive sensitivity was quantified by gage factors corresponding to low ( ε < 0.25%) and high ( ε > 0.3%) strain regimes. Such gage factors were 4.83 (for ε < 0.25%) and 13.2 (for ε > 0.3%) for composites containing multiwall carbon nanotubes only in the polypropylene matrix. The composites containing multiwall carbon nanotubes in the matrix and fibers presented higher piezoresistive sensitivity, with average gage factors of 9.24 ( ε < 0.25%) and 14.0 ( ε > 0.3%). The higher sensitivity to strain and damage for a specific material architecture was also evident during cyclic and constant strain loading programs and is attributed to the preferential localization of multiwall carbon nanotubes in the hierarchical composite.

Chaotic dynamics of a non-autonomous nonlinear system for a smart composite shell subjected to the hygro-thermal environment

In this research, nonlinear dynamic behaviors of multiscale composites doubly curved shells have been investigated by employing multiple scales Perturbation Method. Three-phase composites shells with polymer/Carbon nanotube/fiber (PCF) according to Halpin–Tsai model have been assumed. The displacement- strain of nonlinear vibration of multiscale laminated doubly curved shells via higher order shear deformation (HSDT) theory and using Green–Lagrange nonlinear shell theory is obtained. The governing equations of composite doubly curved shell have been derived by implementing Hamilton’s principle and shell considered to be simply supported. For investigating correctness and accuracy, this paper is validated by other previous researches. Finally, bifurcation diagram, phase portraits and Poincare maps are investigated. The results indicate different dimensionless force; curvature ratio and kind of distribution pattern have strong influence on nonlinear vibration control of the composite multiscale doubly curved shell.

Multiscale composites based on a nanoclay-enhanced matrix and E-glass chopped strand mat

The present work aimed at studying the effect of amino-silanized Na+-montmorillonite nanoclay in various matrix weight ratios (1–7 wt% at a step of 2 wt%) on the mechanical and dry sliding wear behaviors of E-glass chopped strand mat/epoxy composites. The successful grafting of organosilane compound onto the Mt surface was confirmed using Fourier-transform infrared spectroscopy, simultaneous thermal analysis, and X-ray diffraction. Out of the fabricated multiscale composites, the best mechanical strengths were obtained in the specimen with 5 wt% amino-silanized Na+-montmorillonite loading, which demonstrated 18%, 38%, and 53% improvement in the tensile, flexural, and compressive strengths, respectively, compared to the neat chopped strand mat/epoxy composite. The results of pin-on-disk wear test exhibited approximately 81% and 58% decrease in the wear rate and coefficient of friction due to the incorporation of 5 wt% amino-silanized Na+-montmorillonite into the chopped strand mat/epoxy composite. Enhanced mechanical properties and wear behavior of multiscale composite filled with the amino-silanized Na+-montmorillonite nanoparticles were observed compared with those of the unmodified montmorillonite/chopped strand mat/epoxy composite. Based on the microscopic examination of fractured and worn surfaces, the possible mechanisms were identified and evaluated.

그래핀이 적용된 자동차 유리의 전기 및 열 특성 연구

For the automotive application, graphene-glass composites were fabricated using E-glass fiber(GF) coated with various types of graphene nanosheets deposited by electrophoretic deposition. Graphene oxide(GO) was first synthesized using a modified Hummer’s method and its subsequent ultrasonic treatment in deionized water produced a stable stop of the GO. Glass fiber was immersed in water and GO suspension near the copper anode. The potential applied between the electrodes caused the GO to move toward the anode. In addition, the GO coated yarn was exposed to hydrazine hydrate at 100℃ to obtain a reduced graphene oxide(rGO) coating yarn. Both GO and rGO coated glass fiber yarns were used to fabricate unidirectional epoxy-based multi-scale composites by passive lay-up. The presence of a conductive rGO coating on glass fiber improves both the electrical conductivity and thermal conductivity of the composite. In addition, rGO-based epoxy-glass composites have been used to improve the dielectric constant, providing the option of using this structure for electromagnetic interference shielding.

Hybrid multi-scale thermoplastic composites reinforced with interleaved nanofiber mats using in-situ polymerization of cyclic butylene terephthalate

Abstract Mechanically flexible electrospun carbon and glass nanofiber mats (i.e., ECNF-mats and EGNF-mats) were prepared by electrospinning followed by thermal treatments; subsequently, a technique was applied to fabricate two types of multi-scale thermoplastic composites, involving infiltration of molten cyclic butylene terephthalate (CBT) followed by in-situ polymerization under compression. For the first composite type, eight conventional carbon fabrics were interleaved with seven ECNF-mats. For the second composite type, eight conventional glass fabrics were interleaved with seven EGNF-mats. Compared to the values acquired from the corresponding control samples without nanofiber mats, the interlaminar shear strength, flexural strength, flexural modulus, and work of fracture acquired from the hybrid multi-scale composite containing ECNF-mats were increased by 32%, 25%, 19%, and 33%, respectively; while the values acquired from the hybrid multi-scale composite containing EGNF-mats were increased by 66%, 43%, 17%, and 64%, respectively. Furthermore, the enhancements of out-of-plane properties were not at the expense of in-plane tensile strength or modulus. The study indicated that the employed fabrication technique could be adopted as an efficient approach to produce polybutylene terephthalate (PBT) thermoplastic composites through in-situ polymerization of CBT oligomer; and the ECNF-mats and EGNF-mats could be utilized as innovative reinforcement fillers for enhancing the performance of structural thermoplastic composites.

Hierarchical Toughening of Nacre‐Like Composites

AbstractReinforced polymer‐based composites are attractive lightweight materials for aircrafts, automobiles, and turbine blades, but still show strength and fracture toughness lower than traditional metals. An interesting approach to address this issue is to fabricate composites with structural features that absorb part of the elastic energy stored in the material during fracture through extrinsic and intrinsic toughening mechanisms behind and ahead of the crack tip, respectively. Inspired by the nacreous layer of mollusk shells, the fracture behavior of multiscale composites that combine intrinsic toughness from a brick‐and‐mortar structure connected through nanoscale mineral bridges and extrinsic toughness arising from a brittle–ductile laminate architecture at the millimeter scale are fabricated and investigated. Such a hierarchical toughening approach increases the dissipated energy by more than 30‐fold during fracture with minimal loss in stiffness and strength. Using simple energy balance arguments and fracture mechanics concepts, guidelines are established for the design of nacre‐like composites with a remarkable combination of stiffness, strength, and toughness. This demonstrates the possibility to controllably introduce toughening mechanisms at different length scales and to thus fabricate hierarchical composites with high fracture resistance in spite of the brittle nature of their main inorganic constituents.

Fabrication and experimental evaluation of vibration and damping in multiscale graphene/fiberglass/epoxy composites

In this paper, the vibration and damping properties of multiscale laminated fiberglass/epoxy composites modified with a wide range of carbon nanofillers, including multiwalled carbon nanotubes, graphene oxide, reduced-graphene oxide and graphene nanoplatelets were examined for use in structural vibration applications. Simultaneous reinforcement of matrix and fibers was carried out via a novel method that combines a nanoparticle spraying process with nanoparticle/epoxy mixture to incorporate nanoparticles for the enhancement of vibration and damping properties of multiscale laminated fiberglass/epoxy composites. The vibration and damping properties as well as morphological, mechanical properties of the glass fiber-reinforced multiscale composites were investigated. Using a forced vibration technique, the frequency-response functions, natural frequencies and damping ratios of the nanocomposites were measured. The experimental results revealed that the damped natural frequencies of the nanocomposites increased with an increase in nanoparticle concentration. However, at higher contents of nanoparticles, the damped natural frequencies decreased and the damping ratio increased.

Fabrication, Characterisation and Multiscale Modelling of an Epoxy Composite of Amine-Functionalized Carbon Nanotubes Included Three Stages of Carbon Fibre

The goal of this research is to analyse the effect that functionalization has on the material characteristics of multiscale carbon epoxy composites, in addition to determining how efficiently carbon nanotubes are distributed throughout the material (CNTs). As part of this experiment, carbon nanotubes, sometimes referred to as CNTs, were incorporated into an epoxy matrix. After that, carbon fibres were woven into the matrix in order to give it more strength. The resulting combination was used to construct unidirectional carbon fibre laminates. This procedure included infusing an epoxy matrix with a certain number of carbon nanotubes that had been amine-functionalized in the ideal manner. The inclusion of CNTs in the resin at a weight percentage of 1.1 had the impact of creating a significant rise in the Young's modulus. This was the result of the presence of CNTs. The flexural modulus showed observable signs of improvement as a direct result of this action. This event took place as a direct consequence of the presence of CNTs inside the system. However, the overall characteristics of the three-phase composites deteriorated when the epoxy resin was loaded with CNTs at a concentration of 1.6 weight percent. In order to do an examination of the mechanical characteristics of multiscale composites. The two different strategies were combined in order to get this result. The results of this investigation shed light on the disparities that exist between the values that were predicted and the values that were actually found in the data. It is hoped that the multiscale composites in question will be used in the aerospace and missile industries in order to investigate the possibility of structural applications.

Ozonization of SWCNTs on thermal/mechanical properties of basalt fiber-reinforced composites

To move forward in large steps rather than in small increments, the community would benefit from a systematic and comprehensive database of multi-scale composites and measured properties, driven by comprehensive studies with a full range of types of fiber-reinforced polymers. The multi-scale hierarchy is a promising chemical approach that provides superior performance in synergistically integrated microstructured fibers and nanostructured materials in composite applications. Achieving high-efficiency thermal conductivity and mechanical properties with a simple surface treatment on single-walled carbon nanotubes (SWCNTs) is important for multi-scale composites. The main purpose of the project is to introduce ozone-treated SWCNTs between an epoxy matrix and basalt fibers to improve mechanical properties and thermal conductivity by enhancing dispersion and interfacial adhesion. The obvious advantage of this approach is that it is much more effective than the conventional approach at improving the thermal conductivity and mechanical properties of materials under an equivalent load, and shows particularly significant improvement for high loads. Such an effort could accelerate the conversion of multi-scale composites into high performance materials and provide more rational guidance and fundamental understanding towards realizing the theoretical limits of thermal and mechanical properties.

Designing the interphase in carbon fiber polymer composites using carbon nanotubes

Experiments are conducted to quantitatively assess the effect of carbon nanotubes (CNTs) on the interfacial properties in carbon fiber/epoxy composites by directly growing CNTs on the surface of carbon fiber (CF). Wetting behavior of single carbon fiber filaments with epoxy matrix before and after CNT grafting is investigated through contact angle measurements. An improvement in wettability is observed after the incorporation of CNTs on the fiber surface. Effect of wettability on the size and properties of interphase is studied through well designed micro-mechanical tests on single fiber composites processed with unsized and CNT grafted carbon fibers. While nanoindentation testing is performed for quantitative determination of interphase size and stiffness, single fiber micro-debond tests are used to evaluate the interfacial shear strength (IFSS) in unsized carbon fiber/epoxy and CNT grafted carbon fiber/epoxy composites. Consistent with the wettability analysis, CNT grafting enhances the size, stiffness and IFSS of CF/epoxy composites. In addition, it is shown that even though larger CNT growth time on the surface of carbon fiber provides thicker interphase region but tends to degrade the stiffness of interphase and IFSS of CNT grafted carbon fiber/epoxy multiscale composites. Scanning electron microscopy (SEM) analysis of pulled-out and debonded fibers reveal different interfacial failure mechanism in the presence and absence of CNTs on the surface of CF. The present study quantitatively shows the presence of an interphase region surrounding the carbon fiber after CNT grafting on their surface. The existence of interphase is important from the view point of structural integrity of composites as it eliminates the unwanted stress concentration at the fiber/polymer interface by gradual transformation of properties from highly stiff fiber to comparatively weaker matrix. Moreover, the present study provides us a tool to design the interphase in hybrid composites as per the requirement of a specific application.

Incorporation of Carbon Nanotubes on Strategically De-Sized Carbon Fibers for Enhanced Interlaminar Shear Strength of Epoxy Matrix Composites

Carbon fiber reinforced polymeric matrix composites are enormously used in aerospace and automotive industries due to their enhanced specific properties. However, the area of interlaminar shear properties still needs investigation so as to produce composites with improved through-the-thickness properties. To improve interlaminar shear properties of these composites, acid-functionalized multiwalled carbon nanotubes were deposited on de-sized carbon fibers through electrophoretic deposition. De-sizing of carbon fabric was performed through three different methods: furnace heating, acidic treatment and chloroform usage. As the acid-treatment provided better results than other two techniques, the acid-de-sized carbon fibers were coated with nanotubes and subsequently incorporated in epoxy matrix to prepare a novel class of multiscale composites using vacuum assisted resin transfer molding technique. Nearly 30% rise in the interlaminar shear strength of the composites was obtained which was credited to the coating of nanotubes on the surface of carbon fibers. The increased adhesion between carbon fibers and epoxy matrix due to mechanical interlocking of nanotubes was found to be the possible reason of improved interlaminar shear properties.

Tunable negative permittivity in nano-carbon coated magnetic microwire polymer metacomposites

While polymer-based metacomposites with embedded ferromagnetic wires have demonstrated metamaterial wave phenomena with potential applications, fine control over the electromagnetic response remains challenging. Our contribution here involves coupling carbon nanotubes (CNT) and graphene oxide (GO) with the wire via electrodeposition and tailoring the dielectric function of the resulting metacomposite by controlling the thickness and morphology of the CNT and degree of thermal reduction in the GO. As the CNT coating thickness is increased, a conversion of dielectric dispersion from Lorentz resonance to Drude plasma oscillation occurs, which is ascribed to the degree of inter-connection between the CNT networks in the coating. Also, the gradual restoration of sp2 domains and thus expansion of the delocalized π-electron network upon GO thermal reduction are responsible for such conversion in the GO-coated wires. Apart from the regulation of negative permittivity mechanism, the nano-carbon coatings also allow control over the dielectric parameters, including negative permittivity magnitude, plasma frequency and scattering rates determined by interfacial conditions, defects and roughness of the hybrid fibers. These outcomes offer an alternative way to obtain tailorable negative permittivity in the magnetic wire metacomposites and integrate the design philosophy of multiscale composites to that of metacomposites.